Optimize #bind

We needed a blinding fast bind method for a recent project the
old one was too slow. After investigation it was discovered that
prototypes bind method would never be fast enough for our project
so long as the inner function references the arguments keyword.

So, we extended prototype with a bindFast method. This method
runs 5 to 10 times faster in IE8, FF3.6 and CHROME 4 than the
original bind. The downside of the bindFast method is that it can
only support a relatively small numbers of arguments.
However, is there anyway that an implementation like this could
make it into Prototype given this limitation? Would anyone ever
pass more than say.. 10 arguments to a function? I don't think I've
ever passed more than 5!
I've attached a test suite. It needs to be run from the same
directory as prototype.js.